Will setting the solar inverter power factor to 0.9 reduce the power generated by the inverter?
Setting an inverter to a power factor of 0.9 lagging WILL NOT reduce power generated by the inverter by 10%.
1) Setting power factor to 0.9 will only affect the real power export when the inverter is operating at > 90% of its capacity which is a very small amount of the time.
2) Being able to set the power factor (reactive power control) allows larger inverter systems to be connected to the grid. It also assists electricity network providers increases the penetration of solar inverter systems a network can handle.
3) A solar inverter system with reactive power control will trip less frequently.
Benefits provided by 2 & 3 far outweight slight Disadvantage of 1.